Home charging losses and smart tarrifs
Discussion
I've had my Kia EV3 for 14 months, Zappi charger and Octopus Intelligent Go.
I knew that AC charging would mean some charging losses, and this has proved to be a fairly consistent 10 to 15 %. That is, getting 10KWh into the battery would take 11-ish KWh from the mains. It's a very consistent loss, whatever "size" charge I do, or however Octopus allocate the charging slots.
Other half has just taken delivery of a Hyundai Inster 02, and the charging losses are way higher - around 30% on a small charge. A 20% top-up (just under 10KWh in the battery) uses just over 13KWh from the mains.
Googling shows other Inster owners reporting similar losses. Apparently the Inster is set up to preheat the battery to 20 degrees on AC charging?
So, you lose up to 3KWh every time you charge the car, plus the normal 10% AC to DC losses.
This makes small charges ridiculously inefficient.
The way Octopus now allocate multiple 30 minute or one hour slots means wasting 2 or 3 KWh heating up the battery during the first slot, then it cools down a bit and needs more heating during the next slot - more waste.
The solution seems to be to only charge the car when it gets low, and ask for a "big" charge.
That goes against the idea of Intelligent Go though, where Octopus want us to charge "little and often" to maximise their ability to off-load cheap electricity.
Do any other cars suffer from this wasteful AC preheating thing? I thought EVs only really did preheating before DC charging, to maximise charge rates and minimise the time spent plugged in.
I knew that AC charging would mean some charging losses, and this has proved to be a fairly consistent 10 to 15 %. That is, getting 10KWh into the battery would take 11-ish KWh from the mains. It's a very consistent loss, whatever "size" charge I do, or however Octopus allocate the charging slots.
Other half has just taken delivery of a Hyundai Inster 02, and the charging losses are way higher - around 30% on a small charge. A 20% top-up (just under 10KWh in the battery) uses just over 13KWh from the mains.
Googling shows other Inster owners reporting similar losses. Apparently the Inster is set up to preheat the battery to 20 degrees on AC charging?
So, you lose up to 3KWh every time you charge the car, plus the normal 10% AC to DC losses.
This makes small charges ridiculously inefficient.
The way Octopus now allocate multiple 30 minute or one hour slots means wasting 2 or 3 KWh heating up the battery during the first slot, then it cools down a bit and needs more heating during the next slot - more waste.
The solution seems to be to only charge the car when it gets low, and ask for a "big" charge.
That goes against the idea of Intelligent Go though, where Octopus want us to charge "little and often" to maximise their ability to off-load cheap electricity.
Do any other cars suffer from this wasteful AC preheating thing? I thought EVs only really did preheating before DC charging, to maximise charge rates and minimise the time spent plugged in.
clockworks said:
Do any other cars suffer from this wasteful AC preheating thing? I thought EVs only really did preheating before DC charging, to maximise charge rates and minimise the time spent plugged in.
My MGS5 will only battery heat if its below (I think 5 Deg C), otherwise even if you switch it on, it ignores your request.It will be much more efficient in the summer, but you don't say if a home charger is being used. I've only used a 3 pin plug at home on my Honda eNy1 since March 2024, and the losses vary wildly depending on the ambient temp.
In summer on a very warm night, the loses are about 5%. On the occasions I've had to charge when it's below freezing (car is charged outdoors), losses are over 25%.
I don't think it does battery pre-heating. Can it be disabled?
On the occasions I've used super fast public DC chargers, the losses are under 5%. Even using just 7kW / 11kW 'fast' chargers with the car's own cable, it's under 10%.
In summer on a very warm night, the loses are about 5%. On the occasions I've had to charge when it's below freezing (car is charged outdoors), losses are over 25%.
I don't think it does battery pre-heating. Can it be disabled?On the occasions I've used super fast public DC chargers, the losses are under 5%. Even using just 7kW / 11kW 'fast' chargers with the car's own cable, it's under 10%.
We are using a Zappi charger, integrated with Octopus. Both cars are "unsupported" by Octopus.
Appreciate that the losses will be lower in the summer.
Seems odd that two new cars from the same manufacturer (Hyundai own Kia) take different approaches to preheating the batteries on AC charging, with Hyundai seemingly doing it up to much higher ambient temperatures
Appreciate that the losses will be lower in the summer.
Seems odd that two new cars from the same manufacturer (Hyundai own Kia) take different approaches to preheating the batteries on AC charging, with Hyundai seemingly doing it up to much higher ambient temperatures
Is there a Winter or Pre-Conditioning setting that can be disabled on the Inster? Might not be for UK market.
Could be worth raising it with Hyundai, although I don't know a way that would be sure to be effective. Our Gen2 Kona had a whole bunch of updates when it went for its first service recently.
I see some owners using reduced kW granny charging saying the battery heater is taking all of the input power!
Could be worth raising it with Hyundai, although I don't know a way that would be sure to be effective. Our Gen2 Kona had a whole bunch of updates when it went for its first service recently.
I see some owners using reduced kW granny charging saying the battery heater is taking all of the input power!
gmaz said:
Octopus is changing the scheduling from the end of the month so this should be less of a problem perhaps?
I'm not aware of any upcoming scheduling changes, just a proposed cap of 6 hours cheap rate for EV charging.House will still get the 6 hours cheap rate overnight, plus cheap rate whenever the car is charging.
Car will get 6 hours of cheap rate in a 24 hour period, at times set by Octopus. Any car charging over the 6 hours will be at peak rates.
It's possible that Octopus might minimise the "start delay" on each slot to make totting up the 6 hours easier, or even switch to longer continuous slots.
I can't see them doing anything that reduces the flexibility of the slots, as it's financially advantageous to them. Working from home, I'll often get a couple of hours cheap rate just after lunchtime, even if I only ask for a 20% charge (16KWh). I guess on some days the wholesale price of electricity can be lower during the day than at night (more solar/wind).
My car needs a full charge once a month, hers needs a full charge every 6 working days. We will plug in 3 or 4 times a week, 6 hours a day is plenty.
As for pre-conditioning settings, I can only find a setting for doing it manually, or automatically if a charger is set as a destination. Same basic options as I've got on my Kia.
clockworks said:
I'm not aware of any upcoming scheduling changes, just a proposed cap of 6 hours cheap rate for EV charging.
House will still get the 6 hours cheap rate overnight, plus cheap rate whenever the car is charging.
Car will get 6 hours of cheap rate in a 24 hour period, at times set by Octopus. Any car charging over the 6 hours will be at peak rates.
It's possible that Octopus might minimise the "start delay" on each slot to make totting up the 6 hours easier, or even switch to longer continuous slots.
I can't see them doing anything that reduces the flexibility of the slots, as it's financially advantageous to them. Working from home, I'll often get a couple of hours cheap rate just after lunchtime, even if I only ask for a 20% charge (16KWh). I guess on some days the wholesale price of electricity can be lower during the day than at night (more solar/wind).
My car needs a full charge once a month, hers needs a full charge every 6 working days. We will plug in 3 or 4 times a week, 6 hours a day is plenty.
As for pre-conditioning settings, I can only find a setting for doing it manually, or automatically if a charger is set as a destination. Same basic options as I've got on my Kia.
You tend to get free slots when there's plenty of clean energy around.House will still get the 6 hours cheap rate overnight, plus cheap rate whenever the car is charging.
Car will get 6 hours of cheap rate in a 24 hour period, at times set by Octopus. Any car charging over the 6 hours will be at peak rates.
It's possible that Octopus might minimise the "start delay" on each slot to make totting up the 6 hours easier, or even switch to longer continuous slots.
I can't see them doing anything that reduces the flexibility of the slots, as it's financially advantageous to them. Working from home, I'll often get a couple of hours cheap rate just after lunchtime, even if I only ask for a 20% charge (16KWh). I guess on some days the wholesale price of electricity can be lower during the day than at night (more solar/wind).
My car needs a full charge once a month, hers needs a full charge every 6 working days. We will plug in 3 or 4 times a week, 6 hours a day is plenty.
As for pre-conditioning settings, I can only find a setting for doing it manually, or automatically if a charger is set as a destination. Same basic options as I've got on my Kia.
Octopus has a graph on your dashboard with a national green line (the Shen Bephard line).
So today for e.g. you will likely get free electricity until tomorrow morning.
It says
"Cut your carbon footprint by using electricity off-peak, and when it's windy and sunny. The graph below forecasts the carbon intensity of the grid, the greener the grid, the greener the graph and the cleaner the energy at that time. The National Green Line indicates when we deem the Low Carbon Score officially green"
Until 5:30am tomorrow: good time to run appliances Great time to run your dishwasher, washing machine, or charge devices. Energy will be cleanest around 1:30pm."
Pistonheadsdicoverer said:
You tend to get free slots when there's plenty of clean energy around.
Octopus has a graph on your dashboard with a national green line (the Shen Bephard line).
So today for e.g. you will likely get free electricity until tomorrow morning.
It says
Free? did I miss something?Octopus has a graph on your dashboard with a national green line (the Shen Bephard line).
So today for e.g. you will likely get free electricity until tomorrow morning.
It says
Pistonheadsdicoverer said:
You tend to get free slots when there's plenty of clean energy around.
Octopus has a graph on your dashboard with a national green line (the Shen Bephard line).
So today for e.g. you will likely get free electricity until tomorrow morning.
It says
"Cut your carbon footprint by using electricity off-peak, and when it's windy and sunny. The graph below forecasts the carbon intensity of the grid, the greener the grid, the greener the graph and the cleaner the energy at that time. The National Green Line indicates when we deem the Low Carbon Score officially green"
Until 5:30am tomorrow: good time to run appliances Great time to run your dishwasher, washing machine, or charge devices. Energy will be cleanest around 1:30pm."
Where do I find this "green line graph" please? I've just had a look in the app, and I can't see anything like that.Octopus has a graph on your dashboard with a national green line (the Shen Bephard line).
So today for e.g. you will likely get free electricity until tomorrow morning.
It says
"Cut your carbon footprint by using electricity off-peak, and when it's windy and sunny. The graph below forecasts the carbon intensity of the grid, the greener the grid, the greener the graph and the cleaner the energy at that time. The National Green Line indicates when we deem the Low Carbon Score officially green"
Until 5:30am tomorrow: good time to run appliances Great time to run your dishwasher, washing machine, or charge devices. Energy will be cleanest around 1:30pm."
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